Wake-up detector

ABSTRACT

The apparatus is a wake-up circuit including a first comparator coupled to an input signal and configured to compare the input signal to a first comparison value. The wake-up circuit includes a second comparator coupled to the input signal and configured to compare the input signal to a second comparison value. The wake-up circuit further includes an exclusive OR gate. A first input of the exclusive OR gate is coupled to an output of the first comparator. A second input of the exclusive OR gate is coupled to an output of the second comparator. The wake-up circuit also includes a tunable charge pump coupled to an output of the exclusive OR gate and configured to convert a signal from the exclusive OR gate to a DC value to wake up a circuit being monitored.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional Application Ser.No. 62/278,899, entitled “Wake-up Detector for Radio Module,” and filedon Jan. 14, 2016, and U.S. Provisional Application Ser. No. 62/290,880,entitled “Wake-up Detector,” and filed on Feb. 3, 2016, each of which isexpressly incorporated by reference herein in its entirety.

BACKGROUND

Field

The present disclosure relates generally to communication systems, andmore particularly, to circuitry for a radio module or other electronicmodule for waking up from a low power mode.

Background

In some cases, it may be advantageous to power down circuitry when thatcircuitry is not in use. Powering down circuitry when that circuitry isnot in use may conserve battery power. In some examples, conservingbattery power may lead to longer battery life. In other examples,conserving battery power may allow a device to use a smaller batterywhile still providing a required battery life.

While it may be advantageous to power down circuitry when not in use,monitoring circuitry needed to determine when to power up the powereddown circuitry will generally continue to consume power. Accordingly, itmay be advantageous to use monitoring circuitry that uses very littlepower to perform the monitoring function. By using low-power monitoringcircuitry and by powering down circuitry that is not in use, batterypower may be conserved.

SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

As discussed above, in some cases, it may be advantageous to power downcircuitry when that circuitry is not in use to conserve battery power.In some examples, conserving battery power may lead to longer batterylife or may allow a device to use a smaller battery while stillproviding a required battery life. As discussed above, while it may beadvantageous to power down circuitry when not in use, monitoringcircuitry needed to determine when to power up the powered downcircuitry will generally continue to consume power. Accordingly, it maybe advantageous to use monitoring circuitry that uses very little powerto perform the monitoring function.

In an aspect of the disclosure, a method and an apparatus are provided.The apparatus is a wake-up circuit including a first comparator coupledto an input signal and configured to compare the input signal to a firstcomparison value. The wake-up circuit includes a second comparatorcoupled to the input signal and configured to compare the input signalto a second comparison value. The wake-up circuit further includes anexclusive OR gate. A first input of the exclusive OR gate is coupled toan output of the first comparator. A second input of the exclusive ORgate is coupled to an output of the second comparator. The wake-upcircuit also includes a tunable charge pump coupled to an output of theexclusive OR gate and configured to convert a signal from the exclusiveOR gate to a direct current (DC) value to wake up a circuit beingmonitored.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example electronic communicationssystem.

FIG. 2 is a set of diagrams illustrating signals that may be used on asingle cable interface between the core module and the radio module.

FIG. 3 is a diagram illustrating an example of wake-up circuitry inaccordance with the systems and methods described herein.

FIG. 4 is a diagram illustrating an example of wake-up circuitry inaccordance with the systems and methods described herein.

FIG. 5 is a diagram illustrating an example of wake-up circuitry inaccordance with the systems and methods described herein.

FIG. 6 is a diagram illustrating an example of wake-up circuitry inaccordance with the systems and methods described herein.

FIG. 7 is a diagram illustrating various voltage signals that may beused in conjunction with the diagram of FIG. 6.

FIG. 8 is a diagram illustrating an example of a configurable chargepump that may be used in the wake-up circuit of FIG. 3.

FIG. 9 is a flowchart illustrating an example method in accordance withthe systems and methods described herein.

FIG. 10 is a flowchart illustrating another example method in accordancewith the systems and methods described herein.

FIG. 11 is a flowchart illustrating another example method in accordancewith the systems and methods described herein.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well-known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

FIG. 1 is a diagram illustrating an example electronic communicationssystem 100. The example electronic communications system 100 includes acore module 102, a radio module 104, and a single cable interface 106.The core module 102 may be an application-specific integrated circuit(ASIC). One example of an ASIC is circuitry that may include one or morecentral processing units (CPUs) or other functionality that may, forexample, be incorporated into a mobile telephone handset or otherelectronic device. For example, the core module 102 may be a mobilestation modem (MSM). In a communications system, such as the electroniccommunications system 100, the core module 102 may be a master circuitin a master circuit/slave circuit configuration. Similarly, the radiomodule 104 may be a slave circuit in a master circuit/slave circuitconfiguration.

The radio module 104 may include one or more transceivers, one or moretransmitters, or one or more receivers. Accordingly, the radio module104 may transmit radio signals, receive radio signals, or provide acombination of transmitting radio signals and receiving radio signals.For example, the radio module 104 may provide transceiver functionalityto a mobile telephone handset or other electronic communication device.The radio module 104 may transmit and receive electronic signals relatedto a voice communication, Internet protocol (IP) data transmission, orother electromagnetic communication.

In some examples, the core module 102 may control the radio module 104.Accordingly, the core module 102 and the radio module 104 may beconnected. In the illustrated example of FIG. 1, the core module 102 andthe radio module 104 are connected using the single cable interface 106.Accordingly, the core module 102 may control the radio module 104 overthe single cable interface 106. The single cable interface 106 may actas a coupler configured to couple a remote wake-up signal between amaster circuit and the slave circuit using at least one connection ofthe fixed set of cable connections. The at least one connection mayfurther couple a second signal between the master circuit and the slavecircuit.

In some examples, the single cable interface 106 may be a singleconnection such as a single wire connection, a single fiber opticconnection, or another single signal connection. Various signals may bemultiplexed over the single cable connection, e.g., the single wireconnection. In other examples, the single cable interface 106 may be asingle cable including a plurality of connections. (In other words,while the systems and methods described herein may generally be appliedto systems using a single wire connection, these systems and methods mayalso be applied to, for example, one or more individual connections in afixed plurality of connections in a single cable.) The single cableinterface 106 may include a plurality of wire connections, fiber opticconnections, other signal connections, or some combination of wireconnections, fiber optic connections, or other signal connectionsbetween the core module 102 and the radio module 104. The single cableinterface 106 may be fixed, however. In other words, there may be afixed number of connections in the single cable interface 106, and itmay not be possible to add additional connections to the single cableinterface 106. It may be necessary, however, to provide additionalfunctionality through the single cable interface 106.

In some examples, electrical power may be provided by a battery orbatteries. Accordingly, electrical power may be limited, e.g., by thesize of the battery. Because electrical power may be limited, it may bedesirable to conserve electrical power, e.g., battery power. In someexamples, in order to conserve electrical power, the radio module 104may be turned off. Turning off the radio module 104 may conserve batterypower, which may allow for longer periods between battery recharges.Turning off the radio module 104 may also allow for the use of a smallerbattery, which may reduce weight. Additionally, in some examples,turning off the radio module 104 may provide for some combination oflonger periods between battery recharges and the use of a smallerbattery.

In a system where the single cable interface 106 is fixed, additionalcircuitry may be needed so that signals from the core module 102 relatedto turning on and off the radio module 104 may be connected over thefixed single cable interface 106. Accordingly, the fixed single cableinterface 106 may allow the core module 102 to control turning on andoff the radio module 104. The additional circuitry may be a wakeupcircuit 108. The wakeup circuit 108 may be needed so that signals fromthe core module 102 may be used to turn on and off the radio module 104,e.g., the radio components 110 in the radio module. In some examples,the systems and methods described herein may use operational signals,e.g., local oscillator (LO) signals, intermediate frequency (IF)signals, radio frequency (RF) control signals, or DC signals transmittedacross the single cable interface to generate local wakeup signals. Inother examples, the systems and methods described herein may usededicated remote wakeup signals transmitted across the single cableinterface to generate local wakeup signals. In either set of examples, asame single cable interface may be used for operational signals andwakeup signals (with the operational signals being used for both in oneset of examples).

In an example, the radio module 104 may be a 60 GHz radio module. Theradio module 104 may be located apart from the core module 102 and maybe turned on and off according to link transactions, e.g., signals sentover the single cable interface 106 to turn the radio module 104 on andoff. From a power perspective, it may be attractive to consume as littlepower as possible during idle periods, such as periods when the radiomodule 104 is not transmitting or receiving. Some example embodimentsdescribed herein allow for an almost complete power down of a radiomodule (or other electronic circuitry). Generally, the only circuitryneeded to be powered up in the radio module 104 may be a low-powersquelch detector module that initiates a wake-up flow when triggered. Inone example, a low-frequency clock may be used. The low-frequency clockmay provide a signal to synchronize circuitry in an example system. Insome examples, the low frequency clock may be turned off and on toindicate when the radio module may sleep and when the radio moduleshould wake up. (The presence of the clock signal may be determinedusing the systems and methods described herein.) Additionally, the lowfrequency clock may be provided by a power supply module in someexamples that include a low speed clock. Additionally, because thefrequency of the clock may be low, further decreases in the power neededto power circuitry that is utilizing the low-frequency clock may bepossible because, generally, circuitry that is clocked slower may useless power when compared to similar circuitry clocked faster.

The triggering mechanism may utilize an existing controller, e.g.,within the core module 102 between the core and radio chips, e.g., onthe radio module 104. Additionally, the triggering mechanism may beactivated by simply delivering specific controller transactions from thecore chip to the radio module 104.

The radio module 104 may get its voltage supply through the single cableinterface 106. The single cable interface may be the cable on which thedata and control signals are delivered from the core module 102 to theradio module 104. To save power during idle periods, a system may switchthe radio power supply off to the radio module 104. Switching the radiopower supply off may provide power savings, but switching the radiopower supply off may require a supply switch on the core side, whichrequires area on a circuit card and which also increases the number ofitems on the bill-of-materials (BOM). Increases in area on a circuitcard and increases in the number of parts may increase cost. Anotheroption is to turn off radio circuitry in the radio module 104. Turningoff radio circuitry may require keeping a wake-up circuit in standbymode in order to respond to a wake-up request.

Some examples described herein allow for a complete power down, e.g., ofthe radio circuitry, e.g., on the radio module 104. Some examples mayalso implement a low-power circuit that keeps sensing the radio module's104 single cable interface 106. The very low-power circuit may initiatea wake-up sequence when triggered by an RF controller in an existinginterface of a communications system. In some examples, the RF controlsignal may be a digital bit sequence, such as a 125 MHz digital bitsequence. Other digital bit sequences, having other frequencies may beused in other examples.

In some examples, the radio module may include a dedicated wake-updetection circuit as is described herein. During power down, generally,all circuitry may be turned off except a dedicated detector and a moduleDC/DC power converter.

In an example, the core module 102 drives a LO signal, e.g., onto thesingle cable interface 106, to the radio module 104. The core module 102may require a stable clock as part of the wake-up sequence, e.g., togenerate the LO signal and synchronize device operation.

In some examples, the core module 102 or other circuitry may divide andstabilize the LO signal before wake-up. The LO signal may be divided andstabilized before wake-up by using filtering and by using detectorhysteresis. In an example, the core module 102 may start driving a 125MHz clock by enabling the RF controller.

In an example, the radio module 104 may identify an RF controllertransaction and asserts a wake-up signal. When the wake-up signal isdetected, the wake-up sequence may begin.

In an example, an existing RF controller, e.g., core module 102, may beconnected to the radio module 104 through a 50Ω coaxial interface, e.g.,single cable interface 106, which may include 50 Ω terminations on bothends. Disconnecting the 50 Ω termination may result in a very highimpedance due to high gate capacitance at the input to comparators 312,314 (see FIG. 3). For wake-up detection purposes it may be useful tomaintain a high impedance load. A high impedance load may increase theamplitude at the detector inputs. In an example, the controlleramplitude may be ˜300 mV peak on a matched load. A higher impedance loadmay result in up to a doubling of amplitude on the load in one example,e.g., ˜600 mV.

FIG. 2 is a set of diagrams 200 illustrating signals that may be used onthe single cable interface 106 between the core module 102 and the radiomodule 104. The set of diagrams 200 include a frequency diagram 202. Asillustrated in the frequency diagram 202, in one example, signals mayinclude DC signals (e.g., a DC voltage), control signals, e.g., centeredat a frequency of 125 MHz, LO, e.g., centered at 7.5 GHz, and IFsignals, e.g., between 13.7 GHz and 17.1 GHz.

The signals illustrated on the frequency diagram 202 may be carried onthe single cable interface 106. One or more of the signals illustratedon the frequency diagram 202 may be used to control a power-up sequenceon the radio module 104 in addition to the signal's primary functionwhen the radio module 104 is transmitting and/or receiving radiofrequency signals. For example, the DC signal illustrated on thefrequency diagram 202 may provide power to the radio module 104 from thecore module 102. In one example, however, the DC signal may also be usedto control a power-up sequence on the radio module 104. In otherexamples, signals in the LO or IF frequency ranges may be used toprovide an LO or an IF signal when the radio module is transmittingand/or receiving radio frequency signals. Additionally, signals in theLO or IF frequency ranges may also be used to control the power upsequence of the radio module 104.

In another example, the control signals may primarily be used to controlthe radio module 104 when the radio module 104 is transmitting and/orreceiving radio frequency signals. The control signals may also be usedto control a power-up sequence on the radio module 104 without addingadditional connections between the core module 102 and the radio module104 on the single cable interface 106, which, as discussed above, may befixed. For example, as illustrated in FIG. 2, a 125 MHz pulse train maybe transmitted over the single cable interface 106 to indicate that theradio module 104 should power up.

FIG. 3 is a diagram illustrating an example of wake-up circuitry 300 inaccordance with the systems and methods described herein. The wake-upcircuitry 300 may be within the radio module 104 discussed with respectto FIG. 1. The diagram of the wake-up circuitry 300 includes RFcircuitry such as an LO 302, an IF generator 304, and an RF controller306. The LO 302 generates an LO signal, e.g., at 7.5 GHz. The IFgenerator 304 generates IF signals, e.g., between 13.7 GHz and 17.1 GHz.The RF controller 306 generates local control signals that may controlthe radio module 104 of FIG. 1 when the radio module 104 is transmittingand/or receiving RF signals. The LO 302, the IF generator 304, and theRF controller 306 are connected to a cable multiplexer (cable mux) 308.The cable multiplexer 308 may receive signals from the core module 102of FIG. 1 over the single cable interface 106. Additionally, the cablemultiplexer 308 may be used to multiplex signals for the LO 302, the IFgenerator 304, and the RF controller 306 from an output of the cablemultiplexer 308. The cable multiplexer 308 may be coupled to aconnection on the single cable interface 106 of FIG. 1.

In the illustrated example of FIG. 3, the input of the RF controller 306is coupled to circuitry 310. The circuitry 310 may be used to generate asignal to wake up the radio module 104 of FIG. 1. The radio module 104may be powered down or partially powered down to conserve electricalpower, e.g., battery power. Accordingly, the radio module may need to bepowered up when the radio module 104 is needed to transmit or receive anRF signal or RF signals.

The circuitry 310 in the illustrated example of FIG. 3 includes twocomparators 312, 314, two configurable references 316, 318, and anexclusive OR gate 320. A signal from the core module 102 (connected bythe single cable interface 106) may be coupled to the comparators 312,314 through an input switch 322, a DC block capacitor 324, and a DC set326 that includes a pair of resistors R1, R2.

The input switch 322 may be used to connect and disconnect the RFcontroller signal from the comparators 312, 314. The input switch 322allows for input isolation for quiet DC calibration. The DC blockcapacitor 324 may be used to filter the RF controller signal to blockany DC value on the RF controller signal. The DC set 326 is a resistordivider. The DC set 326 includes two resistors R1, R2 that act as avoltage divider. The DC set 326 may be used to superimpose a particularDC value onto the filtered RF control signal, e.g., after the DC blockcapacitor 324. The particular DC value superimposed by the DC set 326 isa function of the two resistor values R1, R2. The DC value in theillustrated example of FIG. 3 is equal to:

$V_{D\; C} = \frac{R_{2}}{R_{1} + R_{2}}$

As illustrated in the example of FIG. 3, the RF controller 306 mayoutput a square wave 328 centered at ground. In other words, the squarewave 328 output from the RF controller 306 in the illustrated examplemay have a voltage swing between a negative voltage and a positivevoltage centered at zero volts. The magnitude of the negative voltageand the magnitude of the positive voltage may be equal or approximatelyequal. The DC block capacitor 324 may remove or reduce any DC value fromthe signal, e.g., the square wave 328 resulting in a signal at 348. TheDC set 326 may be used to adjust the signal after filtering by the DCblock capacitor so that the signal, e.g., a square wave 330, swingsbetween a positive voltage, such as V_(DD), and a ground voltage, e.g.,0 volts.

The comparator 312 may compare the input signal to a configurablereference 316. For example, an output of the configurable reference 316may be coupled to an input of the comparator 312. More specifically, inthe illustrated example of FIG. 3, the output of the configurablereference 316 is coupled to the negative input of the comparator 312.When the voltage of the input signal is higher than the output voltageof the configurable reference 316 an output 350 of the comparator 312will be high. The comparators 312, 314 may provide hysteresis duringoperation of the wake-up circuit 300. In some examples, the hysteresismay decrease the incidence of false positive results at the output ofthe comparators 312, 314.

As illustrated in FIG. 3, each comparator 312, 314 has a configurablereference 316, 318. These configurable references 316, 318 may serve twopurposes. First, the configurable references 316, 318 may be used to seta comparator offset. A minimum allowed reference may be determined byshorting inputs to the comparators 312, 314 and setting the reference toa minimum value that always achieves ‘0’ output level. Second, theconfigurable references 316, 318 may be used to determine a detectionthreshold. Different references may be used in different environments,e.g., different source supplies, cable lengths, and/or noise.Accordingly, the different references may allow the circuit of FIG. 3 tocompensate for different amplitudes due to different source supplies,cable lengths, and noise.

Similarly, the comparator 314 may compare the input signal to aconfigurable reference 318. For example, an output of the configurablereference 318 may be coupled to an input of the comparator 314. Morespecifically, in the illustrated example of FIG. 3, the output of theconfigurable reference 318 is coupled to the positive input of thecomparator 314. When the voltage of the input signal is lower than theoutput voltage of the configurable reference 318 an output of thecomparator 314 will be high.

The outputs 350, 352 of the comparators 312, 314 may be combined usingan exclusive-OR gate 320. The exclusive OR gate 320 has a “true” output(“1”/“high”) when one, and only one, of the inputs to the exclusive ORgate 320 is true. Accordingly, the output of the exclusive OR gate 320is high when either of the comparators 312, 314, has a high output, butboth of the comparators 312, 314 do not have high outputs. Thus, theexclusive OR gate 320 may be used to combine “mutually exclusive”successive comparisons to a single signal, e.g., a pulse train. Theoutput of the exclusive OR gate 320 is low when both of the comparators312, 314 have a low output 350, 352 and when both of the comparators312, 314 have high outputs.

In an example, hysteresis in the comparators 312, 314 may be used fornoise immunity and mismatch correction. Additionally, tuning theconfigurable references 316, 318 may allow for some control ofconversion speed between when a signal is received and when a localturn-on signal is generated because changes in the voltage beingcompared to the square wave 328 made by changing the configurablereferences 316, 318 may impact when switching occurs. (Earlier switchingmay allow for faster conversion speed.)

The square wave 328 (after filtering and DC leveling set) may becompared to the configurable references 316, 318 by the comparators 312,314, respectively. The comparator 312 outputs a square wave 332. Thecomparator 314 outputs a square wave 334. When the square wave 332 andthe square wave 334 are combined in the exclusive OR gate 320, thewaveform 354 results. As illustrated in FIG. 3, square wave 332 andsquare wave 334 may be out of phase with each other such that thewaveform 346 is at a high value for a large percentage of the time and alow value only briefly, e.g., generally when the square waves 332, 334are switching. The configurable charge pump 336 includes a pair ofcurrent sources 338, 340. Accordingly, the configurable charge pump 336may provide a current that may be used to convert the waveform 354 to aDC value. Charge and discharge fluctuations may generally still be onthe signal, but may be filtered out by the capacitor 342. The capacitor342 may filter out any high-frequency component to the waveform 346.Accordingly, coupling the waveform 346 to the configurable charge pump336 and the capacitor 342 may result in a waveform 346.

One or more components, including the comparators 312, 314; configurablereferences 316, 318; exclusive OR gate 320, charge pump 336, capacitor342, or inverter 344, may act as a wake-up signal generator configuredto generate a local wake-up signal at the slave circuit based ondetecting the remote wake-up signal coupled between the master circuitand the slave circuit and wake up the slave circuit with the localwake-up signal. Generally, the wake-up signal generator may includeseveral of these components in order to generate the local wake-upsignal.

The output of the exclusive OR gate 320, e.g., represented by thewaveform 354, may control the configurable charge pump 336. In oneexample, the outputs of both the comparators 312, 314 may initially bothbe low. Accordingly, both inputs to the exclusive OR gate 320 may be lowand the output of the exclusive OR gate 320 may initially be low. Whenthe output of the exclusive OR gate 320 is low the current supply 338 inthe charge pump may drive current to a capacitor 342. Accordingly, thecapacitor 342 may be charged by the current from the current source 338.

When an input signal is detected, the input to the comparator 312 maybegin to toggle above the positive thresholds for the comparator 312.Similarly, when an input signal is detected, the input to the comparator314 may begin to toggle below the negative thresholds for the comparator314. Accordingly, the outputs to the comparators 312, 314 begin totoggle and the output of the exclusive OR gate 320 toggles accordingly.

Generally, the output of the exclusive OR gate 320 may be high longerthan it is low when the output of the exclusive OR gate 320 is toggling,as illustrated by the waveform 354. When the output of the exclusive ORgate 320 is high, the current source 338 is off. The current source 340in the configurable charge pump 336 may then discharge the capacitor 342as discussed below. When the current source 340 discharges the capacitor342, the output voltage of the charge pump 336 may decrease.

When the capacitor 342 is discharged through the current source 340 ofthe configurable charge pump 336, the voltage of the waveform 346 fallsto a low input value (e.g., below the dotted line between ground andV_(DD)). Accordingly, the input to the inverter 344 may be a valid lowinput and the output of the inverter 344 (generally after some delaythrough the inverter 344) may rise from a logic low value to a logichigh value as illustrated by a waveform 347. The inverter 344, mayconvert the configurable charge pump output to a valid digital level. Inanother example, the output buffer may be an inverter.

FIG. 4 is a diagram illustrating an example of wake-up circuitry 400 inaccordance with the systems and methods described herein. The wake-upcircuitry 400 may be within the radio module 104 discussed with respectto FIG. 1. The diagram of FIG. 4 includes RF circuitry, some of which isalso illustrated in FIG. 3, such as the LO 302, the IF generator 304,and the RF controller 306. As discussed above with respect to FIG. 3,the LO 302 generates the LO signal, the IF generator 304 generates theIF signals, and the RF controller 306 generates control signals. The LO302, the IF generator 304, and the RF controller 306 are connected to acable multiplexer 308. The cable multiplexer 308 may receive signalsfrom the core module 102 of FIG. 1 over the single cable interface 106.Additionally, the cable multiplexer 308 may be used to multiplex signalsfor the LO 302, the IF generator 304, and the RF controller 306 from anoutput of the cable multiplexer 308. In the illustrated example of FIG.4, the input of the LO 302 is coupled to circuitry that may be used togenerate a signal to wake up the radio module 104 of FIG. 1. The inputof the LO 302 may be coupled to the core module 102 over the singlecable interface 106. The core module 102 may be coupled to the energydetector 406 through the input switch 406. In another example, the inputof the IF 304 is coupled to the circuitry, e.g., instead of the input ofthe LO 302. The input of the IF generator 304 may be coupled to the coremodule 102 over the single cable interface 106. The core module 102 maybe coupled to the energy detector through an input switch 408. Thecircuitry in the illustrated example of FIG. 4 includes an energydetector 402. The energy detector 402 may detect energy from an LOsignal input to the LO 302 from the core module 102. In another example,the energy detector 402 may detect energy from an IF signal input to theIF generator 304 from the core module. The presence of energy from an LOsignal or an IF signal, as determined by the energy detector 402, mayprovide an indication that the radio module 104 should wake up. Theoutput of the energy detector 402 may be filtered by a capacitor 342 andbuffered by an inverter 404. The inverter 404 may provide some amount ofhysteresis. Hysteresis is a time-based dependence of a system's outputon present and past inputs. Hysteresis may be used in an electroniccircuit to prevent unwanted rapid switching. Accordingly, the hysteresisin the inverter 404 may help to prevent false positives from the energydetector 402.

One or more components, including the energy detector 402, the capacitor342, or the capacitor 404, may act as a wake-up signal generatorconfigured to generate a local wake-up signal at the slave circuit basedon detecting the remote wake-up signal coupled between the mastercircuit and the slave circuit and wake up the slave circuit with thelocal wake-up signal. Generally, the wake-up signal generator mayinclude several of these components in order to generate the localwake-up signal.

The LO 302 or the IF generator 304 may output a sinusoidal signal 414centered at ground. Energy from the sinusoidal signal 414 may bedetected by the energy detector 402. The presence of energy from thesinusoidal signal 414, as detected by the energy detector 402, may be anindication that the radio module 104 should wake up. (The inverter ofFIG. 3 may also have hysteresis in some examples.)

FIG. 5 is a diagram illustrating an example of wake-up circuitry 500 inaccordance with the systems and methods described herein. The wake-upcircuitry 500 may be within the radio module 104 discussed with respectto FIG. 1. The diagram includes RF circuitry, some of which is alsoillustrated in FIGS. 3 and 4, such as the LO 302, the IF generator 304,the RF controller 306, the cable multiplexer 308, and the input switch322. The wake-up circuitry 500 provides an example of circuitry 500 thatallows for a wake-up signal at an arbitrary frequency, e.g., not the LOfrequency, the IF frequency, or the RF control frequency. (The LOfrequency, the IF frequency, or the RF control frequency may be used inconjunction with one or more of the examples with respect to FIGS. 3-4,as described above.)

The input of the cable multiplexer 308 may be coupled to circuitry 502.For example, the input of the cable multiplexer 308 may be coupled tothe circuitry 502 through an input filter 504 and through the inputswitch 322. The input filter 504 illustrated in FIG. 5 may be aband-pass filter. The band-pass filter may be in parallel with themultiplexer 308. Selection of a frequency range of the band-pass filtermay allow for the use of an arbitrary frequency other than the LOfrequency, the IF frequency, or the RF control frequency. For example,the frequency range of the band-pass filter may be selected to match thedesired arbitrary frequency for the wake-up signal.

The circuitry 502 in the illustrated example of FIG. 5 includes theenergy detector 402, which was first discussed with respect to FIG. 4.The energy detector 402 may detect energy from the LO signal, the IFsignal, or the RF controller signal, depending on the state of the cablemultiplexer 308, i.e., depending on which signal input is selected atthe multiplexer and routed to the output of the multiplexer. Generally,the energy detector 402 may be used when either the LO signal or the IFsignal are selected. Some examples may select the RF control signals,however. Energy being detected by the energy detector 402 may provide anindication that the radio module 104 should wake up. The output of theenergy detector 402 may be filtered by the capacitor, 342, and bufferedby an inverter 404. Additionally, the inverter 404 may provide someamount of hysteresis. The hysteresis may help to prevent false positivesfrom the energy detector 402.

The LO 302, the IF generator 304, or the RF controller may output asinusoidal signal 508 centered at ground. Energy from the sinusoidalsignal 508 may be detected by the energy detector 402. The presence ofenergy from the sinusoidal signal 508 may be an indication that theradio module 104 should wake up.

FIG. 6 is a diagram illustrating example wake-up circuitry 600 inaccordance with the systems and methods described herein. The wake-upcircuitry 600 may be within the radio module 104 discussed with respectto FIG. 1. The diagram illustrates an example that may use a DC signalfrom the single cable interface 106 to make a determination to wake upthe radio module 104 of FIG. 1. A DC signal from the single cableinterface 106 may be connected to a comparator 604 through a pair ofresistors R₃, R₄. The pair of resistors R₃, R₄ form a voltage dividerthat may divide the DC signal, V_(DD). The divided voltage is referredto as V_(SUP) in FIG. 6.

$V_{SUP} = \frac{R_{4}}{R_{3} + R_{4}}$

The voltage divided DC signal produced, V_(SUP), may be an input to apositive input line of the comparator 604. A low-power reference 602 mayprovide a voltage reference, V_(REF), to the negative input of thecomparator 604. Accordingly, V_(SUP) and V_(REF) may be compared by thecomparator 604. An output of the comparator may be generated based onthe comparison of V_(SUP) and V_(REF). In some examples, a decrease inV_(DD) may be used to signal that a radio module 104 should be poweredup, and more particularly that the radio components 110 should power up.In some other examples, a decrease in V_(DD) may be used to signal apower up. In some other examples, a slight reduction in V_(DD), e.g.,during power down, followed by an increase to nominal voltage on V_(DD)may be used to initiate power up. In still other examples, a slightincrease in V_(DD), e.g., during power down, followed by a decrease tonominal voltage on V_(DD) may be used to initiate power up.

The output of the comparator 604 may be buffered by an inverter 606 thatmay also provide hysteresis to help filter out noise that may causeinadvertent or unwanted changes to the output of the comparator 604. Oneor more components, including the low-power reference 602, thecomparator 604, or the inverter 606, may act as a wake-up signalgenerator configured to generate a local wake-up signal at the slavecircuit based on detecting the remote wake-up signal coupled between themaster circuit and the slave circuit and wake up the slave circuit withthe local wake-up signal. Generally, the wake-up signal generator mayinclude several of these components in order to generate the localwake-up signal.

FIG. 7 is a diagram 700 illustrating various voltage signals that may beused in conjunction with the diagram of FIG. 6. During a power downstate of the radio module, V_(DD) may still be active. Assuming V_(DD)is a positive voltage, the voltage V_(SUP) may be higher than thevoltage V_(REF). Accordingly, the output of the comparator 604 may behigh, and the output of the inverter 606 may be low when the radiomodule 104 is in a power down state. When the radio module 104 of FIG. 1is to be powered up, the core module 102 may drop the voltage V_(DD)momentarily. When the voltage V_(DD) is momentarily dropped, the voltageV_(SUP) will also momentarily drop, as indicated in FIG. 7. When thevoltage V_(SUP) is lower than the voltage VREF the output of thecomparator 604 will transition to a low value, and the output of theinverter 606 will transition to a high value. When the voltage V_(DD) isthen raised, the voltage V_(sup) will also rise as indicated in FIG. 7.When the voltage V_(SUP) is higher than the voltage VREF the output ofthe comparator 604 will transition to a high value, and the output ofthe inverter 606 will transition to a low value.

FIG. 8 is a diagram illustrating an example configurable charge pump 336that may be used in the wake-up circuit of FIG. 3. Recall from thediscussion of FIG. 3 that the configurable charge pump 336 includes thecurrent source 338 and the current source 340. A PMOS transistor 802 mayprovide the current source 338 illustrated in FIG. 3. The PMOStransistor 802 is coupled to a voltage, V_(DD), and controlled by theinput, IN. When IN is low, the PMOS transistor 802 is on, and currentmay flow through the PMOS transistor 802.

The current source 340 may be provided by NMOS transistors 810, 812.When IN is high, and the switch in component 808 is active, the NMOStransistors 810 are active. The NMOS transistors 812 are controlled bythe signal rfc, which may be a function of a control input (ctrl) andV_(CC) depending on the state of switches in the component 808. Theinverters 804, 806 may invert and buffer the control input (ctrl).Accordingly, the rfc signal may be equal to the control signal (ctrl).Alternatively, depending on the state of the switches in the component808, rfc may be a low value based on an inversion of V_(SS) throughinverter the 806.

As discussed above, the output of the exclusive OR gate 320, e.g.,represented by the waveform 354, may control the configurable chargepump 336. In one example, the outputs of both the comparators 312, 314may initially both be low. Accordingly, both inputs to the exclusive ORgate 320 may be low and the output of the exclusive OR gate 320 mayinitially be low. The current supply 338 may be provided by the PMOStransistor 802. The PMOS transistor 802 may connect V_(DD) to thecapacitor 342 when the PMOS transistor 802 is on. The PMOS transistor802 may be on when the output of the exclusive OR gate 320 is low.Accordingly, the capacitor 342 may be charged with current from theconnection to V_(DD).

When an input signal is detected, the input to the comparator 312 maybegin to toggle above the positive thresholds for the comparator 312.Similarly, when an input signal is detected, the input to the comparator314 may begin to toggle below the negative thresholds for the comparator314. The outputs of the comparators 312, 314 begin to toggle and theoutput of the exclusive OR gate 320 toggles accordingly.

As discussed above, generally, the output of the exclusive OR gate 320may be high longer than it is low when the output of the exclusive ORgate is toggling. When the output of the exclusive OR gate 320 is high,the PMOS transistor 802 is off. The NMOS transistor(s) 810, 812 in theconfigurable charge pump 336 may then discharge the capacitor 342 andthe voltage across the capacitor 342 may decrease.

In one example, the configurability of the configurable charge pump 336is, at least in part, due to the use of a parallel array of multipleNMOS transistors, e.g., the NMOS transistors 810, 812. The number ofNMOS transistors 810, 812 used, the size of the NMOS transistors 810,812 used, or a combination of both number and size may control the slopeof a voltage decrease across the capacitor 342. The number of NMOStransistors 810, 812 used may be selectable. (The NMOS transistors 810may be the primary transistors used to configure the charge pump. Insome examples, the NMOS transistors 812 may generally be on at the sametime and may be used to enable or disable each of the potential currentpaths to V_(SS).)

A voltage decrease across the capacitor 342 is illustrated in thewaveform 346. Using a larger number of NMOS transistors 810, 812 orlarger NMOS transistors 810, 812 may increase the speed of the dischargefrom the capacitor 342 because more transistors or larger transistorsmay generally carry more current than fewer transistors or smallertransistors. Each gate of each NMOS transistor 810 may be controlled byone or more control lines: nctrl[0], nctrl[1], nctril[2], nctril[3]. Theexample control lines nctrl[0], nctrl[1], nctril[2], nctril[3] may beconnected through switches (illustrated as a single switch) to eitherthe exclusive OR 320 output, which is an input of the configurablecharge pump, e.g., “IN” in FIG. 8. The connection to IN may be used whenthe NMOS transistors 810 is enabled and the NMOS transistor is intendedto contribute to the discharge of the capacitor 342. Alternatively, theexample control lines nctrl[0], nctrl[1], nctril[2], nctril[3] may beconnected to ground (or a low output from the inverter 806), e.g., whenthe NMOS transistors 810 is disabled. The NMOS transistors 812 may beused to enable or disable the current path to V_(SS).

The enabled NMOS transistors 810 and the single PMOS transistor 802 maybe connected to the exclusive OR gate 320 output (“IN” in FIG. 8). Theslope on waveform 346 may be based on the discharge of the capacitor342. The slope of the discharge of the capacitor 342 may depend on theratio of PMOS transistors 802 to NMOS transistors (or the ratio ofcurrents through the PMOS transistors 802 to NMOS transistors).

The configurable charge pump 336 may convert the comparators' 312, 314signal, e.g., pulse train (waveform 346) to a DC value (346). Theconfigurable charge pump 336 may be tunable. The PMOS transistor 802 andthe tunable NMOS transistor(s) 810, 812 may adjust charge and dischargepath relationships, allowing slower or faster pulse-DC conversion. Forfaster detection or compensation, a larger NMOS device (or more NMOStransistors 810, 812) may be used. If false alarms occur, a smaller NMOSdevice (or fewer NMOS transistors) may be used to slow the mechanism'sresponse. For calibration, each comparator 312, 314 may be calibratedseparately.

In some examples, an embodiment serves as a low-power wake-up detectorof <50 uA current consumption that is embedded in a radio module, e.g.,60 GHz radio module. The low-power wake-up detector may be keptoperating during power down mode while the rest of the chip may beturned off. The low-power wake-up detector's operation may be based on asquare wave signal of 125 MHz (e.g., square wave 328 of FIG. 3) from amatched 50Ω source which is used to initiate a power up sequence. Someexamples may eliminate an external onboard power switch in the core edgebecause the radio module 104 does not need to be powered down using aswitch using the systems and methods described herein. The systems andmethods described herein may still allow for a deep power down mode ofthe radio module 104 with very low current consumption.

Some examples of wake-up circuitry (300) include a first comparator(312) coupled to an input signal (348). The first comparator (312) isconfigured to compare the input signal (348) to a first comparison value(316). The example includes a second comparator (314) coupled to theinput signal (348). The second comparator (314) is configured to comparethe input signal (348) to a second comparison value (318). The exampleincludes an exclusive OR gate (320). A first input of the exclusive ORgate (320) is coupled to an output (350) of the first comparator. Asecond input of the exclusive OR gate (320) is coupled to an output(352) of the second comparator. The example includes a configurablecharge pump (336) coupled to an output of the exclusive OR gate (320)and configured to convert a signal, e.g., a pulse train (354) from theexclusive OR gate (320) to a DC value (346) to wake up a circuit beingmonitored. (As described herein, the “DC value” waking up a circuitbeing monitored includes, for example, the output of the exclusive ORgate 320 as well as level shifted, filtered, or otherwise processedversions of the DC value.)

The example may include a buffer (344) configured to convert the DCvalue to a digital voltage level (347). The buffer (344) may be aninverter (344). The example may further include an input switch (322)configured to isolate the input signal for DC calibration. The examplemay further include a DC block capacitor (324) coupling the input switch(322) to the input signal (328). The example may further include a DCset circuit (326).

Some example wake-up circuits include a fixed set of cable connections(106) to couple a remote wake-up signal (328) between a master circuit(102) and the slave circuit (104) using at least one connection of thefixed set of cable connections (106). The slave circuit (104) detectsthe remote wake-up signal (328) coupled between the master circuit (102)and the slave circuit (104). The slave circuit (104) generates a localwake-up signal (354, 346, 347) based on detecting the remote wake-upsignal (328) coupled between the master circuit (102) and the slavecircuit (104). The example wakes up the slave circuit (104) based on thelocal wake-up signal (354, 346, 347).

The at least one connection further couples a second signal (328)between the master circuit (102) and the slave circuit (104). (The firstsignal may be the LO, IF, or RF control signals generated to power upthe radio module. The second signal may be the LO, IF, or RF controlsignals generated during operation of the radio module.)

The example may couple the second signal (328) between the mastercircuit (302) and the slave circuit (304) for at least a period of timewhen the slave circuit (304) is awake. The example may compare an inputsignal (348) to a first comparison value (326) to generate a firstcomparison result (350). The example may compare the input signal (348)to a second comparison value (318) to generate a second comparisonresult (352). The example may combine the first comparison result (350)and the second comparison result (352) to generate a signal, e.g., apulse train (354).

In an example, detecting the remote wake-up signal (328) may furtherinclude detecting energy from the remote wake-up signal using an energydetector (402). In an example, a remote wake-up signal includes a DCvoltage (V_(DD)). In an example, detecting the remote wake-up signal(328) further includes detecting a DC voltage (V_(DD), V_(SUP)). In anexample, the remote wake-up signal includes an RF control signal (306).In an example, the remote wake-up signal includes an IF signal (304). Inan example, the remote wake-up signal includes an LO signal (302). In anexample, the remote wake-up signal selectively includes one of an RFcontrol signal (306), an IF signal (304), or an LO signal (302). In anexample, a cable multiplexer (308) may select one of the RF controlsignal (306), the IF signal (304), or the LO signal (302) as the remotewake-up signal. Additionally, an example may filter (324, 504) theremote wake-up signal (302, 304, 306).

FIG. 9 is a flowchart 900 illustrating an example method in accordancewith the systems and methods described herein. The method may beimplemented in wake-up circuitry (300) to wake up a powered down circuit(104). Block 902, compares (312) an input signal (348) to a firstcomparison value (316) to generate a first comparison result (350). Thecompared input value may be an LO signal (302), IF signal (304), or RFcontrol signal (306). The compared input value may be DC filtered by thecapacitor 324 and DC set by the resistors R₁ and R₂

Block 904, compares (314) the input signal (348) to a second comparisonvalue (318) to generate a second comparison result (352). The comparedinput value may be an LO signal (302), IF signal (304), or RF controlsignal (306). The compared input value may be DC filtered by thecapacitor 324 and DC set by the resistors R₁ and R₂.

Block 906, combines (320) the first comparison result (350) and thesecond comparison result (352) to generate a signal, e.g., a pulse train(354). The first comparison result (350) and the second comparisonresult (352) may be combined using the exclusive OR gate 320, or otherlogic circuitry.

Block 908, converts (336) the signal (354) to a DC value (346). Thesignal, e.g., a pulse train, may be converted by the configurable chargepump 336 that may include the current sources 338, 340.

Block 910, wakes up the powered down circuit (104) based on the DC value(346). For example, the DC value (346) or a digital version of the DCvalue (347) may be used to wake a radio module 104. As described herein,the term DC value, as used in the claims, includes the DC value (346) aswell as filtered, DC shifted, or otherwise processed versions of the DCvalue (346).

In some examples, the method may further include buffering (344) the DCvalue (346) to convert the DC value to a digital voltage level (346).Buffering (344) the DC value (346) may include using an inverter tobuffer (344) the DC value (346). Some examples may include switching(322) the input signal to isolate the input signal for DC calibration.

FIG. 10 is a flowchart 1000 illustrating an example method in accordancewith the systems and methods described herein. The method may beimplemented in a wake-up circuitry (300, 400, 500, 600) to wake up apowered down circuit (104). Block 1002 couples a remote wake-up signal(328) between a master circuit (102) and the slave circuit (104) usingat least one connection of the fixed set of cable connections (106). Theat least one connection (106) further couples a second signal betweenthe master circuit (102) and the slave circuit (104). The second signalmay be coupled between the master circuit (102) and the slave circuit(104) for at least a period of time when the slave circuit (104) isawake.

Block 1004 detects, at the slave circuit (104), the remote wake-upsignal (328) coupled between the master circuit (102) and the slavecircuit (104). In some examples, detecting the remote wake-up signal(328) may include detecting energy from the remote wake-up signal usingan energy detector (402). The remote wake-up signal may be a DC voltage(V_(DD)). Accordingly, in one example, detecting the remote wake-upsignal may include detecting the DC voltage (V_(DD)). In anotherexample, the remote wake-up signal may be an RF control signal (306). Inanother example, the remote wake-up signal may be an IF signal (304). Inanother example, the remote wake-up signal may be an LO signal (302).The remote wake-up signal may selectively be one of an RF control signal(306), an IF signal (304), or an LO signal (302). In one example,detecting the remote signal may include selecting (308) one of the RFcontrol signal (306), the IF signal (304), or the LO signal (302) as theremote wake-up signal (328). Some examples may filter (324, 504) theremote wake-up signal.

Block 1006 generates a local wake-up signal (346, 412) at the slavecircuit (104) based on detecting the remote wake-up signal (328) coupledbetween the master circuit (102) and the slave circuit (104). The remotewake-up signal (328) may be generated by circuitry described withrespect to FIGS. 3-6 and FIG. 8.

Block 1008 wakes up the slave circuit (104) based on the local wake-upsignal (346, 412). A wake-up signal (346, 412) generated by circuitrydescribed with respect to FIGS. 3-6 and FIG. 8 may be used to wake upcircuitry such as the radio module 104 of FIG. 1.

FIG. 11 is a flowchart 1100 illustrating an example method in accordancewith the systems and methods described herein. The method of FIG. 11 maybe used with the method of FIG. 10. The method of FIG. 11 includes asubset of the steps of the method of FIG. 9, which may be applied to themethod of FIG. 10. The method may be implemented in wake-up circuitry(300) to wake up a powered down circuit (104). More particularly, theflowchart 1100 of FIG. 11 relates to detecting the remote wake-up signal(328). Block 1102 compares (312) an input signal (348) to a firstcomparison value (316) to generate a first comparison result (350).

Block 1104 compares (312) the input signal (348) to a second comparison(314) value to generate a second comparison result (352).

Block 1106 combines the first comparison result (350) and the secondcomparison result (352) to generate a signal, e.g., a pulse train signal(354).

In some examples, wake-up circuitry (300) includes a means for comparing(312) an input signal to a first comparison value (316) to generate afirst comparison result (350). The example includes a means forcomparing (318) the input signal to a second comparison value (318) togenerate a second comparison result (352). The example includes a meansfor combining (320) the first comparison result (350) and the secondcomparison result (352) to generate a pulse train signal (354). Theexample includes a means for converting (336) the pulse train signal toa DC value (346). The example includes a means for waking up (346) acircuit (104) based on the DC value (346).

The example may include means for buffering (344) the DC value (346) toconvert the DC value (346) to a digital voltage level (347). In someexamples, the means for buffering (344) the DC value (346) may be aninverter. The example may include means for switching (322) the inputsignal to isolate the input signal for DC calibration. The example mayinclude means to DC filter (324) the input signal to generate a DCfiltered input signal (348). The example may include means for DCsetting (326) the DC filtered input signal (348).

Some examples include means for coupling (106) a remote wake-up signal(328) between a master circuit (102) and the slave circuit (104) usingat least one connection (106) of the fixed set of cable connections(106). The at least one connection (106) further couples a second signal(328) between the master circuit (102) and the slave circuit (104). Theexample includes means for detecting (300), at the slave circuit (104),the remote wake-up signal (328) coupled between the master circuit (102)and the slave circuit (104). The example includes means for generating(320) a local wake-up signal (346) at the slave circuit (104) based ondetecting the remote wake-up signal (328) coupled between the mastercircuit (102) and the slave circuit (104). The example includes meansfor waking up (346) the slave circuit (104) based on the local wake-upsignal (346).

The example may include means for comparing (312) an input signal to afirst comparison value (316) to generate a first comparison result(350). The example may include means for comparing (314) the inputsignal to a second comparison value (318) to generate a secondcomparison result (352). The example may include means for combining(320) the first comparison result (350) and the second comparison result(352) to generate a signal, e.g., a pulse train signal (354).

The example may include means for selecting (308) one of the RF controlsignal (306), the IF signal (304), or the LO signal (302) as the remotewake-up signal. Additionally, the example may include means forfiltering (324, 504) the remote wake-up signal (328).

The systems and methods described herein may allow for the same cableconnection, e.g., DC, control, LO, or IF, to be used for a wakeup signaland for a DC, control, LO, or IF connection, respectively. Furthermore,in some examples, the systems and methods described herein may allow forthe same signals, e.g., DC, control, LO, or IF, to be used as a wakeupsignal and for a DC signal, control signal, LO signal, or IF signal,respectively.

It is understood that the specific order or hierarchy of blocks in theprocesses/flowcharts disclosed is an illustration of exemplaryapproaches. Based upon design preferences, it is understood that thespecific order or hierarchy of blocks in the processes/flowcharts may berearranged. Further, some blocks may be combined or omitted. Theaccompanying method claims present elements of the various blocks in asample order, and are not meant to be limited to the specific order orhierarchy presented.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but is to be accorded the full scope consistentwith the language claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” The word “exemplary” is used hereinto mean “serving as an example, instance, or illustration.” Any aspectdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects. Unless specifically statedotherwise, the term “some” refers to one or more. Combinations such as“at least one of A, B, or C,” “one or more of A, B, or C,” “at least oneof A, B, and C,” “one or more of A, B, and C,” and “A, B, C, or anycombination thereof′ include any combination of A, B, and/or C, and mayinclude multiples of A, multiples of B, or multiples of C. Specifically,combinations such as “at least one of A, B, or C,” “one or more of A, B,or C,” “at least one of A, B, and C,” “one or more of A, B, and C,” and“A, B, C, or any combination thereof′ may be A only, B only, C only, Aand B, A and C, B and C, or A and B and C, where any such combinationsmay contain one or more member or members of A, B, or C. All structuraland functional equivalents to the elements of the various aspectsdescribed throughout this disclosure that are known or later come to beknown to those of ordinary skill in the art are expressly incorporatedherein by reference and are intended to be encompassed by the claims.Moreover, nothing disclosed herein is intended to be dedicated to thepublic regardless of whether such disclosure is explicitly recited inthe claims. The words “module,” “mechanism,” “element,” “device,” andthe like may not be a substitute for the word “means.” As such, no claimelement is to be construed as a means plus function unless the elementis expressly recited using the phrase “means for.”

What is claimed is:
 1. A wake-up circuit comprising: a first comparatorcoupled to an input signal and configured to compare the input signal toa first comparison value; a second comparator coupled to the inputsignal and configured to compare the input signal to a second comparisonvalue; an exclusive OR gate, a first input of the exclusive OR gatecoupled to an output of the first comparator, a second input of theexclusive OR gate coupled to an output of the second comparator; and atunable charge pump coupled to an output of the exclusive OR gate andconfigured to convert a signal from the exclusive OR gate to a directcurrent (DC) value to wake up a circuit being monitored.
 2. The wake-upcircuit of claim 1, further comprising a buffer configured to convertthe DC value to a digital voltage level.
 3. The wake-up circuit of claim2, wherein the buffer comprises an inverter.
 4. The wake-up circuit ofclaim 1, further comprising an input switch configured to isolate theinput signal for DC calibration.
 5. The wake-up circuit of claim 4,further comprising a DC block capacitor coupling the input switch to theinput signal.
 6. The wake-up circuit of claim 5, further comprising a DCset circuit.
 7. A method to wake up a circuit, the method comprising:comparing an input signal to a first comparison value to generate afirst comparison result; comparing the input signal to a secondcomparison value to generate a second comparison result; combining thefirst comparison result and the second comparison result to generate asignal; converting the signal to a direct current (DC) value; and wakingup the circuit based on the DC value.
 8. The method of claim 7, furthercomprising buffering the DC value to convert the DC value to a digitalvoltage level.
 9. The method of claim 8, further comprising bufferingthe DC value using an inverter.
 10. The method of claim 7, furthercomprising switching the input signal to isolate the input signal for DCcalibration.
 11. The method of claim 10, further comprising DC filteringthe input signal to generate a DC filtered input signal.
 12. The methodof claim 11, further comprising DC setting the DC filtered input signal.13. A wake-up circuit comprising: means for comparing an input signal toa first comparison value to generate a first comparison result; meansfor comparing the input signal to a second comparison value to generatea second comparison result; means for combining the first comparisonresult and the second comparison result to generate a signal; means forconverting the signal to a direct current (DC) value; and means forwaking up a circuit based on the DC value.
 14. The wake-up circuit ofclaim 13, further comprising means for buffering the DC value to convertthe DC value to a digital voltage level.
 15. The wake-up circuit ofclaim 14, wherein the means for buffering the DC value comprises aninverter.
 16. The wake-up circuit of claim 13, further comprising meansfor switching the input signal to isolate the input signal for DCcalibration.
 17. The wake-up circuit of claim 16, further comprisingmeans for DC filtering the input signal to generate a DC filtered inputsignal.
 18. The wake-up circuit of claim 17, further comprising meansfor DC setting the DC filtered input signal.
 19. An apparatus to wake upa slave circuit in a system, the apparatus comprising: a couplerconfigured to couple a remote wake-up signal between a master circuitand the slave circuit using at least one connection of the fixed set ofcable connections, the at least one connection further coupling a secondsignal between the master circuit and the slave circuit; a detectorconfigured to detect, at the slave circuit, the remote wake-up signalcoupled between the master circuit and the slave circuit; and a wake-upsignal generator configured to generate a local wake-up signal at theslave circuit based on detecting the remote wake-up signal coupledbetween the master circuit and the slave circuit and wake up the slavecircuit with the local wake-up signal.
 20. The apparatus of claim 19,wherein the second signal is coupled between the master circuit and theslave circuit for at least a period of time when the slave circuit isawake.
 21. The apparatus of claim 19, wherein the detector is furtherconfigured to: compare an input signal to a first comparison value togenerate a first comparison result; compare the input signal to a secondcomparison value to generate a second comparison result; and combine thefirst comparison result and the second comparison result to generate asignal.
 22. The apparatus of claim 19, wherein the detector comprises anenergy detector.
 23. The apparatus of claim 19, wherein the remotewake-up signal comprises a direct current (DC) voltage.
 24. Theapparatus of claim 23, wherein the detector is further configured todetect a direct current (DC) voltage.
 25. The apparatus of claim 19,wherein the remote wake-up signal comprises a radio frequency (RF)control signal.
 26. The apparatus of claim 19, wherein the remotewake-up signal comprises an intermediate frequency (IF) signal.
 27. Theapparatus of claim 19, wherein the remote wake-up signal comprises alocal oscillator (LO) signal.
 28. The apparatus of claim 19, furthercomprising a selection component configured to select the remote wake-upsignal from a radio frequency (RF) control signal, an intermediatefrequency (IF) signal, or a local oscillator (LO) signal.
 29. Theapparatus of claim 28, wherein the RF control signal comprises a digitalbit sequence.
 30. The apparatus of claim 29, further comprising a filterconfigured to filter the remote wake-up signal.